Door lock assembly

ABSTRACT

A latch bolt assembly for a door lock is provided which contains a latch bolt and a dead latch intercoupled to one another through a rack and pinion assembly. The mechanism is such that both the latch bolt and the dead latch may be retracted together through a linkage intercoupled to the pull rod of the doorknob mechanism. When the door is closed, the dead latch is held retracted by a striker plate on the door frame as the latch bolt is received in the cavity in the striker plate. This action not only causes the dead latch to restrain the latch bolt against retraction, as is the case in the usual prior art assemblies, but it also causes the latch bolt to be further extended into the cavity in the striker plate so as to increase its throw and thereby to make it more difficult for the door to be forced by jimmying it away from the frame.

United States Patent 1191 Millett DOOR LOCK ASSEMBLY James A. Millett, 18143 Fivestone Ct., Fountain Valley, Calif. 92708 22 Filed: Mar. 28, 1974 21 Appl. No.: 455,576

[76] Inventor:

[56] References Cited UNITED STATES PATENTS 9/1918 Taylor 292/164 11/1967 Neary et a1. 292/164 Primary E.mminerAlbert G. Craig, Jr. Attorney, Agent, or Firm-Jessup & Beecher [57] ABSTRACT A latch bolt assembly for a door lock is provided which contains a latch bolt and a dead latch intercoupled to one another through a rack and pinion assembly. The mechanism is such that both the latch bolt and the dead latch may be retracted together through a linkage intercoupled to the pull rod of the doorknob mechanism. When the door is closed, the dead latch is held retracted by a striker plate on the door frame as the latch bolt is received in the cavity in the striker plate. This action not only causes the dead latch to restrain the latch bolt against retraction, as is the case in the usual prior 'art assemblies, but it also causes the latch bolt to be further extended into the cavity in the striker plate so as to increase its throw and thereby to make it more difficult for the door to be forced by jimmying it away from the frame.

6 Claims, 6 Drawing Figures DOOR LOCK ASSEMBLY BACKGROUND OF THE INVENTION Door locks are known to the prior art which include a latch bolt and a dead latch positioned adjacent to one another and spring-biased to an extended position. In the prior art assemblies, when the door knob is turned, both the dead latch and the latch bolt are retracted together against the spring bias. However, when the door is closed, the latch bolt is received in the cavity in the striker plate on the door frame, and the dead latch is held retracted by the striker plate. This causes the dead latch to restrain retraction of the latch bolt in the prior art assemblies for security purposes.

The lengths of the latch bolt projecting from the edge of the door into the cavity in the striker plate is usually referred to as the throw of the latch bolt. Currently, the throw ofa usual latch bolt is of the order of one-half inch. It has been found, however, that this throw is not sufficient to render the door immune against its being forced open by a jimmying action. It is clear that lengthening of the throw of the latch bolt is certainly desirable from the standpoint of security, because the longer the throw of the latch bolt the more difficult it is to jimmy the door. However, in the prior art locks, there is a limit to the throw of the latch bolt because of the geometry of the locks, and of the manner in which they are mounted in the doors.

The mechanism of the present invention overcomes the problem, however, by providing an intercoupling between the dead latch and the latch bolt, so that when the dead latch is retracted by the striker plate with respect to the latch bolt, it not only restrains retraction of the latch bolt, but it actually increases the projection of the latch bolt into the cavity of the striker plate, so that latch bolt throws of one inch or better are easily accomplished without the need for any changes in the geometry of the lock itself.

An advantage of the mechanism of the invention is that it is simple and straightforward in its concept, so that it can be constructed at relatively low cost. Also, the mechanism of the invention can be fitted into existing locks without any need to change the geometry of the locks themselves.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective representation of a door lock assembly which includes a dead latch and a latch bolt, and in which the two elements are intercoupled by a rack and pinion sub-assembly in accordance with the concepts of the invention;

FIG. 2 is a view, like FIG. I, but showing the dead latch retracted, and illustrating the increased projection of the latch bolt upon the retraction of the dead latch:

FIG. 3 is an exploded perspective representation of the various components which make up the mechanism of the invention;

FIG. 4 is a perspective representation of the mechanism of the invention in an assembled condition, but with the dead latch removed so that the interrelationship of the other components may be more clearly illustrated;

FIG. 5 is a side elevation of the assembly of the invention; and

FIG. 6 is a plan view of a sub-assembly which is included in the mechanism of the invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT As shown in FIG. 1, the mechanism of the invention may be incorporated into a usual lock assembly. The lock assembly of FIG. 1 includes an inner doorknob l0, and an outer doorknob 12, the two doorknobs being positioned on opposite sides of a door 14. The doorknobs l0 and 12 operate a latch bolt 16 and an adjacent dead latch 18, both of which extend through an end plate 20, which is attached to the edge of the door by screws, such as the screws 22.

Whenever either of the doorknobs 10 or 12 is operated, both the latch bolt 16 and the dead latch 18 are retracted together, so that the door may be opened. Also, when the door is closed, the bevelled edge of the latch bolt 16 engages the striker plate mounted on the adjacent portion of the door frame so that the latch bolt and the dead latch may both be retracted. As the door is fully closed, the latch bolt 16 is received in the cavity of the striker plate, but the dead latch 18 is held in a retracted position by the striker plate. In accordance with the present invention, this retraction of the dead latch 18 relative to the latch bolt, as shown in the view of FIG. 2, actually causes the latch bolt 16 to extend its projection a substantial amount, so that it extends an additional distance into the cavity in the striker plate, when the door is closed, so as to enhance the security of the lock.

As shown in FIG. 3, the latch bolt 16 has an inner end portion of reduced thickness, and a toothed rack 16A is formed on the rear portion. The rear portion of the latch bolt 16 has a flat surface, as does the adjacent forward portion 168. A channel is formed in the forward portion 168 to receive the dead latch 18. The dead latch 18 also has a flat surface, as shown, and it has a toothed rack 18A formed in that surface. The dead latch 18 is received in the channel formed on the surface of portion 163 of the latch bolt 16, with its toothed rack 18A facing the toothed rack 16B of the latch bolt.

A coil spring 30 is mounted in a well in the rear end of the latch bolt 16, and a coil spring 32 is mounted in a well in the rear end of the dead latch 18. These coil springs engage the end wall of a tubular housing 34, when the assembly is received in the housing, andbias the forward ends of the latch bolt 16 and the dead latch 18 through the aperture in the end plate 20.

A flat rectangular-shaped carriage 36 is received between the latch bolt 16 and dead latch 18 is position, such as best shown in FIG. 4. The carriage 36 also defines a longitudinal channel along one of its faces which is aligned with the channel in the latch bolt 168, as shown in FIG. 4. The dead latch 18 is received in the two aligned channels, with its toothed rack facing inwardly. A pinion, or ratchet, 40 is rotatably mounted in the carriage 36, and it engages both the toothed rack 16A and the toothed rack 18A.

A flat rectangular linkage member 42 fits into a channel formed on the opposite face of the carriage 36, as best shown in FIG. 6. A pawl, or cog, 42A is formed at the forward edge of the linkage member 42. A longitudinal slot is formed in the linkage member 42, and a longitudinal projection 42B extends partially along the slot. An upstanding projection 36A is formed in thecarriage 36, and it extends upwardly into the slot. A coil spring 50 is fitted around the projection 423 to be interposed between the end of the slot in the linkage 42 and the projection 36A. This spring serves to bias the pawl 42A into a ratchet engagement with the pinion 40.

The linkage 42 has a rear portion 428 which extends through the end wall of the housing 34 to be coupled to the pull rod of the lock mechanism associated with the knobs and 12.

Whenever either knob 10 or 12 is turned, the pull rod pulls the linkage 42 to free the pawl 42A from the pinion 40, and to move the carriage 36, and the latch bolt 16 and dead latch 18, as a unit into their retracted positions, so that the door may be opened. When the door is closed, without turning the knobs, the bevelled edge of the latch bolt 16 engages the side of the striker plate, and the latch bolt is moved inwardly into the housing 34. During this action, the pawl 42A engages the pinion 40, and does not permit the pinion to rotate, so that the dead latch is also retracted. Therefore, the dead latch is also moved into its retracted position by the movement of the latch bolt. At no time will the pinion 40 and paw] 42A allow'the dead latch to extend out further than the latch bolt.

However, when the latch bolt moves into the cavity in the striker plate, the pinion 40 turns by ratchet action against the pawl 42A, since the dead latch is held retracted by the striker plate. The latch bolt, accordingly, by spring bias moves into the cavity to its fully extended position, such as shown in FIG. 2. The latch bolt is restrained in its fully extended position by the ratchet action of the pawl against the pinion, until the knob 10 or 12 is again turned to pull the linkage member 42 to release the pawl 42A from the pinion 40, so that the assembly may be withdrawn into the housing 34, with the pawl 40 rotating freely to re-align the latch bolt 16 and the dead latch 18.

The invention provides, therefore, a simple latch bolt assembly, which includes an improved mechanism which can be easily incorporated into existing locks, and which serves to increase the throw of the latch bolt as the dead latch is actuated to restrain the retraction of the latch bolt.

It will be appreciated that while a particular embodiment of the invention has been shown and described, modifications may be made. his intended in the claims to cover the modifications which fall within the true spirit and scope of the invention.

What is claimed is:

l. A latch bolt assembly comprising: a housing; a latch bolt slidable in said housing and having a toothed rack formed at the inner end thereof; a dead latch slidable in said housing adjacent said latch bolt and having a toothed rack formed at the inner end thereof in facing relationship with the toothed rack of said latch bolt; a carriage slidable in said housing and interposed between the inner end of the latch bolt and the dead latch; a pinion rotatably mounted on said carriage and engaging the toothed racks formed on said latch bolt and on said deadlatch; a linkage member coupled to said carriage to move said carriage in said housing and thereby withdraw said dead latch and latch bolt from an extended position to a retracted position; a pawl formed on the outer end of said linkage member in position to engage the pinion in a ratchet relationship therewith to permit rotation of said pinion in one direction and to arrest rotation of said pinion in the other direction when the linkage member is released; and resilient means interposed between said linkage member and said carriage normally to bias said pawl into engagement with said pinion.

2. The assembly defined in claim 1, and which includes coil springs interposed between the end wall of said housing and said latch bolt and dead latch normally to bias said latch bolt and said dead latch to their extended position.

3. The assembly defined in claim 1, in which said carriage has a flat rectangular configuration and defines a channel at one side thereof for receiving said linkage member, and in which said linkage member has a flat rectangular configuration and has an elongated rear portion extending through the end wall of said housing.

4. The assembly defined in claim 3, in which said linkage member has an elongated slot formed therein, and said carriage has an upstanding projection extending into the slot, and in which said resilient means comprises a coil spring positioned in the slot and interposed between one end of the slot and said projection.

5. A latch bolt assembly comprising: a housing; a latch bolt slidable in said housing; a dead latch slidable in said housing; a carriage slidable in said housing inter-' posed between the inner ends of said latch bolt and said dead latch and coupled to said dead latch and to said latch bolt; a linkage member coupled to said carriage to move said carriage in said housing thereby to withdraw said dead latch and said latch bolt from an extended position to a retracted position; a toothed rack formed at the inner end of said latch bolt; a toothed rack formed at the inner end of said dead latch in facing relationship with the toothed rack of said latch bolt; and a pinion rotatably mounted on said carriage and engaging the toothed racks formed on said latch bolt and said dead latch.

6. The assembly defined in claim 5, and which includes a pawl formed on the outer end of said linkage member in position to engage the pinion in a ratchet relationship to permit rotation of the pinion in one direction and to arrest rotation of the pinion in the other direction when the linkage member is released, and resilient means interposed between said linkage member and said carriage normally to bias said pawl into engagement with said pinion. 

1. A latch bolt assembly comprising: a housing; a latch bolt slidable in said housing and having a toothed rack formed at the inner end thereof; a dead latch slidable in said housing adjacent said latch bolt and having a toothed rack formed at the inner end thereof in facing relationship with the toothed rack of said latch bolt; a carriage slidable in said housing and interposed between the inner end of the latch bolt and the dead latch; a pinion rotatably mounted on said carriage and engaging the toothed racks formed on said latch bolt and on said dead latch; a linkage member coupled to said carriage to move said carriage in said housing and thereby withdraw said dead latch and latch bolt from an extended position to a retracted position; a pawl formed on the outer end of said linkage member in position to engage the pinion in a ratchet relationship therewith to permit rotation of said pinion in one direction and to arrest rotation of said pinion in the other direction when the linkage member is released; and resilient means interposed between said linkage member and said carriage normally to bias said pawl into engagement with said pinion.
 2. The assembly defined in claim 1, and which includes coil springs interposed between the end wall of said housing and said latch bolt and dead latch normally to bias said latch bolt and said dead latch to their extended position.
 3. The assembly defined in claim 1, in which said carriage has a flat rectangular configuration and defines a channel at one side thereof for receiving said linkage member, and in which said linkage member has a flat rectangular configuration and has an elongated rear portion exTending through the end wall of said housing.
 4. The assembly defined in claim 3, in which said linkage member has an elongated slot formed therein, and said carriage has an upstanding projection extending into the slot, and in which said resilient means comprises a coil spring positioned in the slot and interposed between one end of the slot and said projection.
 5. A latch bolt assembly comprising: a housing; a latch bolt slidable in said housing; a dead latch slidable in said housing; a carriage slidable in said housing interposed between the inner ends of said latch bolt and said dead latch and coupled to said dead latch and to said latch bolt; a linkage member coupled to said carriage to move said carriage in said housing thereby to withdraw said dead latch and said latch bolt from an extended position to a retracted position; a toothed rack formed at the inner end of said latch bolt; a toothed rack formed at the inner end of said dead latch in facing relationship with the toothed rack of said latch bolt; and a pinion rotatably mounted on said carriage and engaging the toothed racks formed on said latch bolt and said dead latch.
 6. The assembly defined in claim 5, and which includes a pawl formed on the outer end of said linkage member in position to engage the pinion in a ratchet relationship to permit rotation of the pinion in one direction and to arrest rotation of the pinion in the other direction when the linkage member is released, and resilient means interposed between said linkage member and said carriage normally to bias said pawl into engagement with said pinion. 